If $x \bigtriangleup y = (4-x)(y)$ and $x \dagger y = x-7y$, find $4 \bigtriangleup (5 \dagger 6)$.
First, find $5 \dagger 6$ $ 5 \dagger 6 = 5-(7)(6)$ $ \hphantom{5 \dagger 6} = -37$ Now, find $4 \bigtriangleup -37$ $ 4 \bigtriangleup -37 = (4-4)(-37)$ $ \hphantom{4 \bigtriangleup -37} = 0$.